Why can't i render smoke with my AMD graphic card
Not currently supported, I'm afraid.

You can see the list of supported features over at the Blender manual

As of Blender 2.78a, October 2016:

Feature                    CPU                 CUDA (NVIDIA GPU)   OpenCL (AMD GPU)

Basic Shading              ✔                   ✔                   ✔

Transparent Shadows        ✔                   ✔                   ✗

Motion Blur                ✔                   ✔                   ✔

Hair                       ✔                   ✔                   ✔

Volume                     ✔                   ✔                   ✗

**Smoke / Fire             ✔                   ✔                   ✗

Subsurface Scattering      ✔                   ✔                   ✗

Open Shading Language      ✔                   ✗                   ✗

CMJ sampling               ✔                   ✔                   ✗

Branched Path integrator   ✔                   ✔                   ✗

Displacement/Subdivision   ✔ (experimental)    ✔ (experimental)    ✔ (experimental)